Endovascular graft system

ABSTRACT

The invention provides an endovascular graft system for repair of aneurysms. The graft system includes a trunk component and first and second leg components. The graft components include graft material supported by a plurality of stents which are spaced apart and affixed to the graft material in a manner that allows articulation of the graft system without excessive wear of the graft material. The stents are formed by intersecting struts which may be tapered to relieve stress. A stabilizing mechanism is provided to stabilize the position of the legs with respect to the trunk when the graft system is deployed.

[0001] This is a continuation of application Ser. No. 09/454,038 filedDec. 3, 1999, the contents of which are hereby incorporated herein byreference.

FIELD OF THE INVENTION

[0002] This invention relates to endovascular graft systems for therepair of aneurysms. In particular, this invention relates to anendovascular graft system for use in repairing abdominal aorticaneurysms.

BACKGROUND OF THE INVENTION

[0003] Aortic aneurysms represent a significant medical problem for thegeneral population. Aneurysms within the aorta presently affect betweentwo and seven percent of the general population and the rate ofincidence appears to be increasing. This form of vascular disease ischaracterized by a degradation in the arterial wall in which the wallweakens and balloons outward by thinning. If untreated, the aneurysm canrupture resulting in death within a short time.

[0004] The traditional treatment for patients with an abdominal aorticaneurysm is surgical repair. This is an extensive operation involvingtransperitoneal or retroperitoneal dissection of the aorta andreplacement of the aneurysm with an artificial artery known as aprosthetic graft. This procedure requires exposure of the aorta throughan abdominal incision extending from the lower border from the breastbone down to the pubic bone. The aorta is clamped both above and belowthe aneurysm so that the aneurysm can be opened and the prosthetic graftof approximately the same size as the aorta is sutured in place. Bloodflow is then reestablished through the prosthetic graft. The operationrequires a general anesthesia with a breathing tube, extensive intensivecare unit monitoring in the immediate postoperative period along withblood transfusions and stomach and bladder tubes. All of this imposesstress on the cardiovascular system. This is a high-risk surgicalprocedure with well-recognized morbidity and mortality.

[0005] More recently, significantly less invasive clinical approaches toaneurysm repair known as endovascular grafting have been proposed. (See,Parodi, J. C., et al. “Transfemoral Intraluminal Graft Implantation forAbdominal Aortic Aneurysms,” 5 Annals of Vascular Surgery, 491 (1991)).Endovascular grafting involves the transluminal placement of aprosthetic arterial graft in the endoluminal position (within the lumenof the artery). By this method, the graft is attached to the internalsurface of an arterial wall by means of attachment devices such asexpandable stents, one above the aneurysm and a second below theaneurysm.

[0006] Although endovascular grafting represents a desirable improvementover traditional surgical repair, current endovascular graft systemssuffer from certain deficiencies. For example, current endovasculargraft systems typically are unsuitable for use in an aneurysm which istortuous. Aneurysms in the aorta create tortuosity as they grow.Aneurysms grow both in diameter and length, thus “pushing” the adjacentupper and lower portions of the arteries upward and downward,respectively. Since the aorta is relatively “fixed” at the renalarteries, the portion of the aorta below and near the renal arteriesbecomes bent and curved in order to accommodate the added length. Asimilar phenomenon occurs below the aneurysm in the iliac arteries,leading to tortuous iliacs. As many as 20% of aortic aneurysms may haveso much tortuosity that they are unable to be fitted with anendovascular graft of this kind. Such systems are unable to conform tothe curved walls of the vasculature due to the tortuosity caused by thegrowing aneurysm.

[0007] A specific problem is the “angulation” or bend in the neck of theaorta, where it meets the upper part of the aneurysm. This angulationmay result in several problems which limit the effectiveness oftraditional endovascular graft systems which do not have designs thatconform to the tortuosity and angulation above the aneurysm. First,since these systems are typically anchored above the aneurysm with astent, a portion of the stent may extend into the blood flow path,creating turbulence which may result in blood clotting. It is well-knownthat in coronary vessels, stents used to treat constrictive lesions mustbe well apposed to the wall of the vessel to prevent the possibility ofthrombosis. Second, a non-conforming upper stent will not place theupper end of the graft in good apposition to the aortic wall, making itdifficult to obtain a good seal with a conventional endovascular graftsystem. Such is illustrated in FIG. 2, showing a generic endovasculargraft attached to a conventional non-conforming expanded metal stent inthe neck of a tortuous aortic neck. Since this conventional stent willnot conform to the tortuosity of the aorta, an upper edge 1 of the stentextends into the blood flow path increasing the chance of thrombosis.Further, a lower edge 2 is not apposed to the wall of the aorta so thatthe graft material 3 affixed to it does not properly seal. A thirdproblem with non-conforming attachment systems is that once placed intortuous or angulated aneurysmal anatomy, they are unstable and can“pop-out” of position. The attachment system shown in FIG. 2 is anexample of an unstable attachment system. Conventional endovasculargraft systems having an attachment system intended to project across andabove the renal artery ostia also pose a different problem since theattachment system obstructs the renal arteries making it difficult, ifnot impossible, to effect a repair on a renal artery once the stent isin place.

[0008] Thus, a need exists for a prosthetic endovascular graft systemwhich will permit stable conformance to bends within an aneurysm, whileproviding a good seal to the vasculature.

[0009] Another challenge for endovascular grafting of aortic aneurysmsrelates to the need for graft systems to be delivered in as small of a“profile” as possible. This has driven the design of most endovasculargrafting systems to be fabricated with very thin-walled graft conduits.This thin walled conduit, usually coupled to an internal supportframework, typically a metallic framework attached to the graft conduiton either the inside or on the outside, is susceptible to “wear andtear” mechanisms arising from the pulsatile blood pressure and flow inthe aorta. Numerous incidences have been reported in the literature ofholes and tears being created in the graft conduit from the cyclic,localized rubbing of the metallic framework against the thin walledgraft conduits of a variety of endovascular grafting systems.

[0010] Thus, a need exists for a prosthetic endovascular graft systemwhich will minimize or eliminate the wearing mechanisms on the tubulargraft conduit, enabling the graft system to be safely utilized inpatients for long periods of time, i.e. several years, without concernof premature failure due to wear.

[0011] Yet another concern of current endovascular graft systems relatesmore specifically to the long-term integrity of metallic stents whichare used for supporting the structure of the graft material. Sinceportions of many of the stents used for graft support are in directinterface with the aorta (and iliac arteries in the case of biluminalendovascular graft systems), the pulsatile forces that cause pulsatilediameter changes on these vessels are transferred to these stentportions. This pulsation in the stents leads to cyclic stressing, andcan cause premature fatigue failure and breakage.

[0012] Thus, a need exists for a prosthetic endovascular graft systemwhich incorporates stents that are designed to minimize cyclic stressesand thus avoid fatigue failure.

SUMMARY OF THE INVENTION

[0013] This invention is an endovascular graft system for use inrepairing aneurysms. In one aspect, the invention is an endovasculargraft system capable of being deployed at a desired location within avessel. The graft system includes an aortic stent having first andsecond ends, a trunk formed of a graft material having an interiorsurface defining a lumen and being affixed to the second end of theaortic stent, and a plurality of stents affixed to and supporting theinterior surface of the trunk, the plurality of stents being spacedapart such that fully unsupported regions of the trunk lie betweenadjacent stents. The graft material of the trunk is affixed to theaortic stent and to the plurality of stents in a manner which limitsmovement of the graft material with respect to the aortic stent and theplurality of stents. The graft material of the trunk may be crimpedtoward the lumen in the unsupported regions between stents. The trunkhas first and second branches configured such that the lumen comprises amain lumen and first and second branch lumens and wherein the pluralityof stents includes a first or mid-stent located in the main lumenbetween the aortic stent and the first and second branch lumens andfurther includes a plurality of second stents located in the first andsecond lumens.

[0014] In another aspect, this invention is a stent for placement in avessel of a patient's vascular system. The stent comprises asubstantially tubular body portion having a plurality of struts, eachstrut having first and second ends and a midpoint located midwaytherebetween, each end of the plurality of struts intersecting with anend of at least one adjacent strut to form a plurality of strutintersections, at least one strut being configured to taper between themidpoint and the first and second ends in a manner that is gradual andsubstantially continuous. The stent has a tubular body portion whichdefines a longitudinal axis and has a first end and a second end. Aplurality of intersecting struts adjacent the first end form asubstantially diamond shape pattern at the first end of the stent and aplurality of intersecting struts adjacent the second end form asubstantially zigzagged pattern at the second end of the stent. Thediamond shaped pattern and zigzagged pattern are connected by aplurality of longitudinal struts which are parallel to the longitudinalaxis of the stent. The strut which is configured to taper may be one orall of the struts which are adjacent the first end of the stent. Thetapering strut may be configured such that the strut tapers from alarger dimension at the midpoint to smaller dimensions at the first andsecond ends or from a small dimension at the midpoint to largerdimensions at the first and second ends.

[0015] In another aspect the invention is a delivery catheter fordelivering and deploying an endovascular graft system at a desiredlocation within a vessel of a patient's vascular system. The catheterincludes a handle and a shaft having a distal end and a proximal end,the proximal end being connected to the handle, the shaft further havingan outer surface and defining an inflation lumen and a guidewire lumen.A balloon is attached at a location spaced from the distal end of thecatheter. The balloon has an interior in fluid communication with theinflation lumen. A transition element is affixed to the balloon. Thetransition element has a distal portion between the balloon and thedistal end of the catheter, the distal portion being configured toprovide increasing stiffness from the distal end of the catheter to theballoon. The shaft, balloon and transition element together form aportion of an inner catheter. An outer sheath defines a lumen whichcontains the inner catheter. The outer sheath is configured to move froman unretracted position to a retracted position and has a distal endpositioned about the balloon when in the unretracted position. Thedistal portion of the transition element may taper outwardly from thedistal end of the catheter to the balloon. The lumen of the outer sheathhas a first diameter at the distal end of the outer sheath which is lessthan the diameter of the balloon when inflated.

[0016] In another aspect, the invention is a delivery catheter fordelivering an endovascular graft system at a desired location within avessel of a patient's vascular system. The delivery catheter includes ashaft. First and second graft components are positioned about the shaft,the first graft component being positioned distally of the second graftcomponent. The first graft component is configured to be deployed in thevessel prior to deployment of the second graft component. Both the firstand second graft components have proximal and distal portions, thedistal portion of the second graft component being configured to bedeployed within the proximal portion of the first graft component. Thecatheter has a retractable sheath which defines a lumen containing theshaft and the first and second graft components. The sheath isconfigured to deploy the first graft component when it is withdrawn afirst distance and to deploy the second graft component when it iswithdrawn a second distance. Means are included for stabilizing theposition of the distal portion of the second graft component withrespect to the proximal portion of the first graft component when thesheath is being withdrawn the second distance.

[0017] In a further aspect the invention is a delivery catheter fordelivering an endovascular graft system at a desired location within avessel of a patient's vascular system. The delivery catheter includes ahandle and a shaft connected to the handle. First and second graftcomponents are positioned about the shaft, the first graft componentbeing positioned distally of the second graft component. The first graftcomponent is configured to be deployed in the vessel prior to deploymentof the second graft component. The first and second graft componentseach have proximal and distal portions, the distal portion of the secondgraft component being configured to be deployed within the proximalportion of the first graft component. The distal portion of the secondgraft component has a fastening element. A retractable sheath defines alumen which contains the shaft and the first and second graftcomponents. The handle is configured to retract the sheath to deploy thefirst graft component when the sheath is retracted a first distance andto deploy the second graft component when the sheath is retracted asecond distance. A stabilizing element connected at one end to thehandle and at another end to the fastening element of the second graftcomponent stabilizes the second graft component with respect to thefirst graft component during deployment. The handle, stabilizing elementand fastening element are configured such that the stabilizing elementis retracted in a manner that disconnects the stabilizing element fromthe fastening element when the second graft component is deployed. Thesecond graft component includes a stent located at the distal portionwhich has an eyelet comprising the fastening element. The stabilizingelement may be a wire.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a diagrammatic view of a portion of a human vascularsystem depicting an abdominal aortic aneurysm which extends from belowthe renal arteries and into the common iliac arteries and which hascaused angulation of the aorta above and below the renal arteries.

[0019]FIG. 2 is a partial view of a conventional Prior Art endovasculargraft system deployed in an angulated aorta such as shown in FIG. 1.

[0020]FIG. 3A is a perspective view of a biluminal endovascular graftsystem of this invention and FIG. 3B is a detailed perspective view ofthe aortic stent, trunk, and branches of the biluminal graft system ofFIG. 3A.

[0021]FIG. 4 is a view of the aneurysm of FIG. 1 with the fully deployedbiluminal graft system of FIG. 3 in place.

[0022]FIG. 5 is a cut-away view of a portion of the biluminalendovascular graft system of FIG. 3 showing support stents inside theconduits of the endovascular graft system.

[0023]FIG. 6A is a perspective view of the aortic stent of thisinvention. FIGS. 6B and 6C show enlarged views of portions of the stent,and FIGS. 6D, 6E, and 6F show details of the cross-sectional shapes ofvarious portions of the stent shown in FIG. 6A. FIGS. 6G and 6H showenlarged partial views of the stent of FIG. 6A in its unexpandedcondition. FIG. 6I shows an enlarged partial view of a prior art stent.

[0024]FIG. 7A shows a side view of the mid-stent of the presentinvention and FIG. 7B shows a top view of the mid-stent.

[0025]FIG. 8 is a perspective view of the iliac stent of the presentinvention.

[0026]FIG. 9 is a perspective view of one leg of the graft system ofFIG. 3A.

[0027]FIG. 10 is a perspective view of a support stent of the presentinvention.

[0028]FIGS. 11A and 11B show steps in the deployment of the aortic stentof the present invention in an angulated aorta.

[0029]FIG. 12 illustrates a view of the delivery system used to insertand deploy a portion of the graft system of the embodiment of FIG. 3.

[0030]FIG. 13 is a view of the delivery system of FIG. 12 with the outersheath retracted.

[0031]FIG. 14 illustrates an enlarged view of a distal portion of thedelivery system of FIG. 12.

[0032]FIGS. 15A and 15B are cross-sectional views taken along lines a-aand b-b of FIG. 13, respectively.

[0033]FIG. 16 is a cross-section view of the handle of the deliverycatheter of FIG. 12.

[0034]FIG. 17 is a partial enlarged view of the distal end of the outersheath of the delivery catheter of FIG. 12.

[0035]FIG. 18 is a partial view of the proximal tapering transitionelement and wire stabilizer of the catheter of FIG. 12.

[0036]FIG. 19 is a perspective view of an alternative embodiment of theaortic stent of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The terms “distal” and “proximal” as used in this specificationrefer to the method of delivery of the graft system, not to thevasculature. The preferred method of this graft system contemplatesadvancement of a catheter in a retrograde manner (i.e., against the flowof blood). Therefore, “proximal” refers to a location closer to thephysician and “distal” refers to a location farther from the physician.The vasculature is referred to with respect to the cranial (closer tohead) and caudal (closer to feet) directions. Also, as used in thisspecification, the term “above”, in the context of relative positioningwith respect to the aneurysm, refers to the region cranial of theaneurysm, for example, within the aorta, whereas “below” refers to theregion of the vasculature caudal of the aneurysm, for example, withinthe common iliac arteries.

[0038] The present invention is a graft system for implantation within alumen in a patient's body. Although the specific embodiments disclosedherein relate to an endovascular graft system for treating a variety ofabdominal aortic aneurysms, it will be understood that the graft systemwill have a broader application and is suitable for use in any bodylumen which may be repaired or reinforced by a graft system.

[0039] The endovascular graft system of this invention may be useful fortreating a variety of aneurysms. For example, a biluminal endovasculargraft system may be used for treating aneurysms that extend close to orinto the common iliac arteries. In these aneurysms there is not asuitable place within the aorta to seat the lower end of a simpletubular graft. Therefore, the graft must be able to extend into eachiliac artery for suitable seating. By “seating” it is meant that thegraft is implanted, fixed, or otherwise secured to the vasculature.

[0040] The graft of the preferred embodiment is supported internally byindividual stents, or support stents, which are themselves connected tothe graft in a manner which secures their position, for example, bysutures. This endovascular graft system is envisioned for use primarilywith aneurysms which would benefit from treatment with a biluminalmulticomponent endovascular graft system. That is, such a graft systemhas an aortic stent capable of fitting into the neck of an aorta whichhas been bent or angulated as a result of an aneurysm. A trunk extendsfrom the aortic stent into the aneurysm. The trunk splits into twobranches into which right and left legs are secured during deployment ofthe graft system across the aneurysm. The right and left legs have iliacstents at their proximal ends for connection with a respective commoniliac artery. However, depending upon the geometry of the aneurysm, thissystem could be useful in other graft system designs such as with aunibody bifurcated graft; a tube graft; or a modular two-piece grafthaving one short segment and one long segment extending from the mainbody of the graft, and a separate leg which can be joined to the shortsegment, as is known to one of skill in the art.

[0041] Turning now to the Figures, the shape of an aneurysm and theplacement and use of the endovascular graft system are described.

[0042]FIG. 1 depicts an aneurysm A in the infrarenal aorta which extendsinto the common iliac arteries. Aneurysm A has caused aorta Ao to becomebent or angulated. The infrarenal aorta is that portion of the aortadisposed between the left and right renal arteries RA and the commoniliac arteries B that branch left and right. No distinction is made inthe figures between elements introduced on the left or the right of thepatient's vasculature. Each common iliac artery branches into internaland external iliac arteries, D and C respectively. External iliac arteryC becomes the femoral artery below the inguinal ligament. Internal iliacartery D is also known as the hypogastric artery.

[0043]FIG. 3A illustrates a biluminal endovascular graft system of thepresent invention. Aortic stent 10 is shown connected to graft material45 forming trunk 12 having two branches 14 and 16. Trunk branches 14 and16 are designed to join with legs 15 and 17, respectively, thus forminga biluminal endovascular graft system. Legs 15 and 17 are designed to bepositioned within branches 14 and 16. In a preferred embodiment, thebranches overlap the legs at least about 1.5 cm. Once positioned, branch14 and leg 15 form conduit 20 and branch 16 and leg 17 form conduit 22as best seen in FIG. 4. The friction of the overlap between the legs andbranches keep conduits 20 and 22 from coming apart. At the caudal orproximal end of legs 15 and 17 are positioned iliac stents 18 and 19.Iliac stents 18 and 19 are sutured within an elongated portion of theconduits at the caudal ends thereof and are sized such that whenexpanded will fix the ends of the conduits within the iliac arteries.

[0044]FIG. 3B illustrates in greater detail the aortic stent, the trunkand its branches. FIG. 4 shows the fully deployed graft system. FIG. 3Bshows that graft material 45 of trunk 12 is joined to aortic stent 10via sutures, shown here as blanket stitches 25. Mid-stent 30 (notvisible within the graft material making up trunk 12) is stitched totrunk 12 via blanket stitches 29 and 35. Point stitches 27 secure thestruts of mid-stent 30. Trunk 12 (having branches 14 and 16) with stent10 comprises a first component of the deliver system. Legs 15 and 17comprise second and third components of the delivery system. Twocomponents of the delivery system (trunk 12 and branches 14 and 16 alongwith stent 10 and leg 15) are loaded into a single delivery catheter anddelivered through one femoral artery into the aorta. Trunk 12 and leg 15are spaced apart and positioned sequentially in the delivery catheter.Aortic stent 10 is moved into the desired position, typically across therenal artery ostia. The catheter is manipulated to withdraw an outersheath which exposes the aortic stent and allows it to expand radiallyso that it seats within the aorta. Further retraction of the outersheath allows trunk 12 with its branches 14 and 16 to expand fully.Right leg 15 of the system is then positioned within the trunk branch 14and delivered from the same delivery catheter, thus forming conduit 20.The third component of the delivery system, left leg 17, is delivered bymeans of a separate delivery catheter from the other femoral artery, upthe iliac artery and into branch 16 of the trunk. Conduit 22 is thusformed and is identical in structure to conduit 20. The length of theoverlap between the branches and legs can be varied by the physician asthe system is delivered. Thus, the length of the system can becustomized to the patient. Radiopaque markers 28 d, 28 e, and 28 f helpposition the upper end of trunk 12 to facilitate proper position andorientation in the aorta, relative to the renal arteries. Marker 28 f ispositioned at the upper end of branch 16 (the ipsilateral branch) toindicate the maximum overlap position for legs 15 and 17, so as toprevent excess overlap, or “stove-piping”. Markers 28 a, 28 b, and 28 care positioned approximately 2 cm above the caudal end of the branches14 and 15. This allows legs 15 and 17 to be positioned with at least aminimal amount of overlap. Marker 28 c is positioned near the outeraspect of the caudal end of branch 16 (the contralateral branch), tofacilitate advancement of a wire and contralateral delivery system intothat branch.

[0045]FIG. 4 illustrates the biluminal endovascular graft system fullydeployed across an aortic aneurysm. Aortic stent 10 is shown conformingto the curvature of the aorta. The femoral artery is entered within thethigh by an arterial incision where the vessel is close to theundersurface of the skin. A guidewire is first endoluminally placed,using conventional techniques to a position in the patient's thoracicaorta, above an aortic aneurysm such as depicted in FIG. 1. The deliverysystem is guided into the aneurysm along this guidewire. The guidewireremains in a fixed position throughout the endoluminal procedure.Conventional angiography techniques are employed to identify theaneurysm and the position of key anatomical structures such as the renaland hypogastric arteries. The components to be delivered in this mannerare in a compressed and folded state in the delivery catheter. That is,the material making up the graft system is maneuvered into position andthen allowed to expand as described below. The delivery system isdescribed in greater detail below with respect to FIGS. 12-18.

[0046]FIG. 5 illustrates the endovascular graft system with portions cutaway to show the internal structure of conduit 20 and branch 16descending from trunk 12. The graft system includes support stents 40within conduits 20 and 22. Typically, these support stents arerelatively short compared to the total length of a leg. The size andspacing of the support stents allows for articulation of the legs of theendovascular graft system without the formation of kinks. In addition,the graft has crimps 41 formed in the spaces between the individualstents in fully unsupported portions of graft material. These crimps actas controlled bending points for the graft, while the individual supportstents 40 hold open the lumen adjacent the crimps 41. Thus, the legs areable to bend or elongate to accommodate bends within the aneurysm andiliac arteries, while maintaining a large open lumen. The support stentsare affixed to graft material 45 by sutures, not shown in FIG. 5.

[0047] The individual components of the implanted endovascular graftsystem are described in further detail below.

[0048] Aortic Stent

[0049] Aortic stent 10 shown in FIGS. 6A-6H is comprised of multipleintersecting struts configured so that there are radially strong cranialand caudal zones 50 and 52 at either end, as depicted in FIG. 6A. FIGS.6B and 6C show enlarged views of portions of the stent. FIGS. 6D, 6E,and 6F show details of the cross-sectional shapes of struts in variousportions of stent 10 along lines d-d, e-e, and f-f, respectively. Thesezones are configured to permit radial expansion and contraction, asdescribed further below. The cranial and caudal zones are configured andmade of materials that exhibit sufficient radial outward force or radialstrength when expanded so that the graft system will be securelyanchored within the aorta above the aneurysm when the stent is deployed.FIG. 6I shows an enlarged portion of a prior art stent with high stressareas.

[0050] The cranial and caudal zones of the aortic stent are connected byan intermediate zone comprising multiple longitudinal struts 55 whichare substantially parallel to a longitudinal axis defined by the tubularaortic stent. This unique three zone configuration of the aortic stentmember is important for several reasons. First, this configurationallows the cranial zone of the stent to be deployed virtuallyindependently of the caudal zone. This is illustrated best by referenceto FIGS. 11A and 11B which show deployment of the aortic stent portionof the graft system in the aorta. For purposes of clarity, the guidewirewhich would be present during deployment is not shown. In FIG. 11A thesheath of delivery catheter 110 has been partially withdrawn to deploycranial zone 50 of stent 10. Cranial zone 50 can be seen to be securelydeployed and seated within the aorta. At this stage of the deliveryprocess blood flowing in the aorta in the direction of arrow 102 is notoccluded. Thus, cranial zone 50 has been deployed and seated within theaorta in the absence of force in the direction of arrow 102 which wouldbe exerted had the blood flow been occluded. As a result, cranial zone50 is deployed precisely where intended.

[0051]FIG. 11B shows a further stage of deployment after the sheath hasbeen withdrawn past caudal zone 52 partially exposing the graft materialof trunk 12. Caudal zone 52 is partially deployed as is trunk 12. It canbe seen that the deployment of caudal zone 52 and trunk 12 has partiallyoccluded the aorta. A force in the direction of arrow 102 begins to beasserted against the graft system and increases as caudal zone 52 andtrunk 12 expands nearer the wall of the aorta. The position of the stentis, however, unaffected by that pressure since the cranial zone 50 ofthe stent has already been fully and securely deployed in the aortabefore any significant pressure caused by occluding the aorta has builtup.

[0052] This constitutes a significant advantage over current graftsystems which utilize traditional self-expanding stents to secure thegraft system in the aorta above the aneurysm. Stents used in thosesystems are relatively short, i.e., approximately 2 cm. Since the upperor cranial end of these stents cannot be deployed independently of thelower or caudal end, the result is that the stent is not seatedsufficiently upon deployment before the aorta is occluded, creating alarge downward force on the partially deployed graft system. Thus, thepressure caused by occlusion of the aorta makes it difficult to properlyposition such graft systems at a desired location with the aorta.

[0053] Another advantage of the three-zoned stent is that thelongitudinal struts of the transition zone between the cranial andcaudal zones allow the stent to adapt to angulation or tortuosity of theaorta and still provide a good seal with the wall of the aorta. Just asthe quarters at each end of a stack of quarters will remain paralleleven if the stack is off-set so will the cranial and caudal zones of thestent remain parallel even though the stent is deployed in a curved ortortuous aorta as in FIG. 4. In contrast, traditional stents tend not toadapt well to tortuous configurations and do not seal well against thewalls of the aorta, as shown in FIG. 2.

[0054] A still further advantage of the three zoned stent is that itresists longitudinal stretching. Thus, proper positioning upondeployment is easier since the stent will not vary in length during orafter delivery by the surgeon.

[0055] The longitudinal struts 55 are sufficiently flexible so that theycan bend, but they do not elongate axially. The radial strength of theregion of the longitudinal struts is lower than the radial strength ofthe caudal or cranial zones due to the configuration of the aorticstent. Radial strength is the force exerted outward (i.e., from thecenter of the stent) by the cranial and caudal zones and theintermediate zone. That is, these different areas exert radial forces onthe vasculature when placed across the aneurysm.

[0056] The aortic stent is preferably self-expanding and is comprised ofa shape memory alloy, such as that described below. The system typicallyis fabricated by laser cutting a tube of shape memory alloy, thenforming the tube to the desired shape.

[0057] As illustrated in FIGS. 6D, 6E, and 6F, the thickness and widthof longitudinal struts 55 is less than that of the struts making up thecaudal or cranial zones. In this manner, longitudinal struts 55 areflexible and conformable and do not interfere with the caudal andcranial zones' ability to expand independent of each other. Thelongitudinal struts maintain a constant distance between the caudal andcranial zones with the result that these zones remain substantiallyparallel to one another even when the aortic stent is bent. Thus, theaortic stent is able to conform to the shape of a tortuous aorticaneurysm and remain longitudinally stable. Conventional stent designswhich allow bending such as a coil stent or articulation also allow thestents to readily elongate. In this invention, the stent does notelongate, thus keeping the graft secure once it is placed into thevasculature.

[0058] Aortic stent 10 is sized to fit the aorta. Large diameter aortaswill require a larger sized graft system, and small diameter aortas willrequire a smaller sized graft system. For example, for a 22 to 27 mmaorta, the stent diameter is preferably 30 mm in diameter. The followingpreferred dimensions for the aortic stent are intended for a 30 mmdiameter device. It is understood that smaller or larger diameter graftsystems would require appropriately larger or smaller dimensions.

[0059] In a preferred embodiment, cranial zone 50 has diamond-shapedcells (i.e., two connected “zigzags”) formed from, for example, cranialstruts 51 a, 51 b, 51 c, and 51 d, and caudal zone 52 has a zigzag shapemade up of caudal struts, for example, 53 a, 53 b, 53 c, and 53 d. Firstapex 50 a of a diamond-shaped cell formed at the intersection of struts51 a and 51 b is shown in detail in FIG. 6B. Apex 50 a is a smooth,uniform width curved region. This shape is cut directly into the stentduring the initial laser cutting, and is maintained during allsubsequent processes of grit blasting, shape setting, andelectropolishing (all described in further detail below). Junction 50 boccurs at the intersection of four cranial struts. Preferably, thejunction of struts is provided with indentations 50 d and 50 e, as shownin FIG. 6C. Second apex 51 b joins longitudinal strut 55.

[0060] Because the aortic stent is larger in its relaxed diameter thanthe diameter of the aorta, there are residual stresses within the strutsof the stent. Also, because the aortic stent rests directly against theaorta, any pulsatile motion of the aorta wall is transferred to thestent. This constitutes a cyclic fatigue stress that is placed onregions of the stent. In particular, in the regions of the stent nearthese intersections, as shown in detail in FIGS. 6B and 6C, have thehighest stresses. To minimize the stresses in these regions, theintersecting regions are designed to maintain uniform beam widths nearwhere the struts intersect. Beam width refers to the width of the strut.Indentation 50 d is laser cut into junction 50 b to maintain a uniformbeam width in the area subject to the highest stress. By designing thejunction between cells in the cranial zone to maintain uniform beamwidths, the stress and strain that would normally build up in aconcentrated spot near the junctures is allowed to “spread out” into theconnecting regions, thereby lowering the peak values of the stresses andstrains in the stent structures. In prior art stents without suchindentations such as shown in FIG. 6I high stress areas j and k canoccur.

[0061] To further minimize the maximum stresses in the struts of theaortic stent, the struts can have a tapering width. In one embodiment,the strut can become wider as it approaches an intersection. This isshown in FIG. 6H. The strut width near the intersections (width a) ispreferably 0.025 cm (0.010 inches), and gradually tapers to a dimensionof 0.0178 cm (0.007 inches) in the mid region of the strut (width b). Bytapering the strut widths, the stresses in the struts adjacent theintersections is spread out further away from the intersection. Thetapering of the strut widths is accomplished during laser cutting of theinitial tube. By tapering the struts in this fashion, there is atrade-off, however. The tubular stent structure becomes less resistantto localized deformations, caused for example, by a protrusion withinthe vessel lumen. This localized deformation leads to a local torsionaltwisting of some of the struts, and therefore, since the struts in thiscase have a significant portion of their length of reduced width, thetorsional rigidity is lowered.

[0062] If maximizing the resistance to localized deformation ispreferred, the struts are preferably maintained at a uniform width, ormost preferably actually have a reverse taper, as is shown in FIG. 6G,wherein the distance a is less than the distance b. For example, thewidth of cranial strut 51 a nearest junction 50 b is about 0.003 cm(0.001 in.) less than the width of the remainder of cranial strut 51 a.Preferably, the strut narrows near any intersection. This is alsoreferred to as a “reverse taper”, and is shown in FIG. 6G. For theaortic stent, the reversed tapered struts are preferably about 0.025 cm(0.010 in.) wide near the intersections, and 0.028 cm (0.011 in.) widenear the middle of the strut. While this reverse taper actually tends toincrease the stresses somewhat near the intersections, this increase isvery small, relative to the decrease in stresses gained by having theside indentations at the intersections, as shown in FIG. 6C, as well asthe uniform width connections as shown in FIG. 6B. And since the reversetaper serves to increase the torsional rigidity of the strut, the stentstructure resists local deformation, and tends to maintain a circulartubular geometry, even if the lumen it is placed within is non-circular.

[0063] By minimizing the stresses in the aortic stent, the risk offatigue fracture of the struts is greatly reduced. This lowered stressdesign also enables the aortic attachment system of the currentinvention to be utilized in a wider range of aorta sizes, and in aortasthat may have high pulsatile diameter variations, while minimizing anyincrease in stress in the member. Additionally, when the aortic stent isdesigned to minimize stresses, any dimensional variations caused byprocessing variations in the laser cutting, grit blasting, orelectropolishing (described below) will result in higher local stressesand strains, but these higher stresses and strains will still be belowcritical levels which could cause premature fracture of the structure.

[0064] An example of the dimensions of an aortic stent useful in thisinvention is one in which the cranial zone is approximately 15 mm long,and the caudal zone is approximately 7.5 mm long. Each zone preferablyhas 14 complete zigzags. Longitudinal struts 55 are approximately 15 mmin length. There are preferably 14 longitudinal struts, corresponding tothe number of zigzags of the caudal and cranial sections. Approximately14 mm of the length of the struts 55 are transitioned to a reducedthickness and width. Caudal and cranial zones 50 and 52 have strutthicknesses and widths between approximately 0.023 and 0.035 cm (0.009in. and 0.014 in.) with gradual tapering strut widths as describedabove. In a preferred embodiment, the struts are narrower nearintersections and wider in the middle of a strut, as illustrated in FIG.6G. The reduced regions of longitudinal struts 55 have strut width andthicknesses between approximately 0.018 and 0.028 cm (0.007 and 0.011in.) The reduced regions of longitudinal struts 55 have their widths cutto a thinner dimension directly from the laser cutting process on theinitial tube. However, in the thickness direction, the laser cut tube issubsequently placed on a support mandrel and is either centerless groundor center-ground with methods known to those skilled in the art.

[0065] Stent 10 is approximately 3 cm in length. It typically isdesirable to “oversize” the stent to assure a good seal and engagementwithin the aorta. A minimum of about 3 to 4 mm oversize is preferred. Itis also expected that tissue ingrowth occurs faster with an exposedstent (as opposed to a stent covered with graft material), leading tolong-term anchoring of the stent. Barbs 58, hooks, or the like may beused to increase the mechanical fixation of the stent to the aorta. Ifbarbs 58 are used, they are preferably placed at the caudal end of thestent, as shown in FIGS. 3 to 6A. However, they could also be placed atthe cranial end. The barbs are preferably sharpened on the end thatengages the aorta.

[0066] For many aneurysms it is necessary to position the aortic stentacross the renal arteries in order to properly anchor the system.Although this may be a desirable way to position an aortic stent toensure that it is properly secured within the aorta, such positioningcan inhibit blood flow into the renal arteries. The aortic stent of thisinvention crosses the renal artery without significantly inhibitingblood flow. Both the design of the stent and the small cross-sectionalarea of the struts prevent significant obstruction of blood flow. Thisminimizes thrombosis and, additionally, provides for subsequent accessto the renal arteries.

[0067] The aortic stent of this invention conforms to a bend ortortuosity in the vessel and does so without any elongation in thestent. That is, it maintains longitudinal integrity unlike a coil orother stents which may bend, but also which can elongate. This isimportant because the aortic stent must stay in the desired position,maintain the seal with the vasculature and prevent the graft from movingaxially.

[0068] When deployed, the caudal and cranial zones of the aortic stentlie against the wall of the vasculature and produce a good seal. Thematerial in these zones is shaped to permit radial expansion andcontraction of the system to conform to the size and shape of the aortaand still maintain sufficient radial force to securely anchor the graftsystem. This shape also permits the caudal and cranial ends of theaortic stent to expand to different diameters. This is an advantage foran aneurysm exhibiting tortuosity. The ability of the stent to conformresults in good seating of the stent in the vasculature so that itcannot move out of position. In addition, the ends of the aortic stentdo not rest away from the aortic wall as in prior art devices (such asthat illustrated in FIG. 2). This can prevent the proper sealing of suchgraft systems and result in thrombosis. It is also contemplated that theobjectives of the present invention can be achieved with a stent made upof multiple zones of high radial strength (such as the cranial andcaudal zones) connected by multiple zones of longitudinal struts (suchas the intermediate zone).

[0069] A further advantage of the present invention is that thelongitudinal struts separating and joining the caudal and cranial zonescan be moved out of the, way in the event that further surgery on therenal arteries becomes necessary. This reintervention would be verydifficult with the aortic stent of a conventional endovascular graftsystem in place across the renal arteries. Such systems typically havetoo many struts to allow them to be moved out of the way for cathetersto pass into the renal arteries Even in the case where the present stentis comprised of longitudinal struts which are not of reduced thicknessor width, they can be easily displaced because of their relatively longlength compared to the length of the caudal or cranial zones.

[0070] Yet another advantage of the aortic attachment system of thisinvention is that there is a lower risk of thrombosis. This is becausethere is less metal and stent structure across the renal arteries thanwith conventional expanded metal stents.

[0071] Mid Stent

[0072] Mid-stent 30 is attached to the inside of the graft (trunk 12)just below the caudal end of aortic stent 10. Mid-stent 30 providessupport and structure to trunk 12 where the graft transitions from asingle lumen to branches 14 and 16. It preferably is formed from a lasercut tube and shape set into a diamond like mesh pattern, as shown inFIGS. 7A and 7B. FIG. 7A shows a side view of the mid-stent, shaped sothat the upper (or cranial) diameter matches that of the aortic stent.FIG. 7B shows a top view of the mid-stent and shows that the caudalportion of the stent is shaped to join branches 14 and 16. Thedimensions of a mid-stent, for example, is approximately 30 mm inlength, comprising a diamond like mesh having struts that areapproximately 7.5 mm long, with 14 circumferentially oriented zigzags.The mid-stent is preferably cut from an initial tube of 0.267 cm ID by0.356 cm OD (0.105 in. ID by 0.140 in. OD).

[0073] The mid stent is shape set on a mandrel with a tapering shape,inducing the tapering contour to the stent. This contour helps create asmooth transition to the graft structure from a single lumen (trunk 12)to two lumens (branches 14 and 16). Thus, the caudal portion has asmaller diameter, or opening, than the cranial portion. Further, thecaudal portion may be formed so that the opening approaches a figureeight shape.

[0074] Since at least a portion of the mid-stent is constrained by thenon-aneurysmal portion of the aorta, this stent too is subjected to thesame pulsatile motion as the aorta and aortic stent. Therefore, thestruts are processed in a manner similar to those in the aortic stent.The intersecting regions of struts have the same shape as those for theaortic stent, and the struts have a reverse taper, (wider at the middleof the strut than near the intersections) similar to the cranial strutsof the aortic stent above.

[0075] Iliac Stents

[0076]FIG. 8 illustrates iliac stent 18 having a series of zigzag strutsconnected together. Iliac stent 18 preferably is formed of threeconnected zigzags. The junction of the struts is similar to thosediscussed in connection with the cranial struts of aortic stent 10 shownin FIGS. 6B and 6C.

[0077] Iliac stents preferably are fabricated from a laser cut tube ofinitial dimension 0.229 cm ID by 0.318 OD (0.090 in. ID by 0.125 in.OD). Like both the aortic stent, and the mid-stent, the struts areprocessed to minimize strain near the strut intersections. The strutsand intersections are similar in design to those in the mid-stent andaortic stent. As in the aorta, the iliac arteries exhibit pulsatile wallmotion, and since the iliac stents would be constrained by the iliacarteries, they will be cyclically stressed, and would therefore benefitfrom lower stress. The struts are preferably 0.0229 cm (0.009 in.) wideadjacent the four strut intersections, and 6 mm long, having a reversetapering strut width similar to that of the aortic stent.

[0078] Also, to minimize the number of different diameter combinationsof graft systems, it is preferred that the iliac stent have an expandeddiameter of 16 mm. when expanded. Similarly, the proximal portion of thegraft material forming the legs is flared, having a diameter of 16 mm.This single diameter for the iliac ends of the graft system would enableits use in iliac arteries having a non-aneurysmal region of a diameterfrom preferably between 8 and 14 mm in diameter. It is also contemplatedthat multiple diameter combinations of iliac stent and graft flare wouldbe desirable.

[0079] Support Stents

[0080]FIG. 9 illustrates one leg of the endovascular graft system,showing iliac stent 18 at the caudal end, and support stents 40, 41, and42. In order to illustrate the relationship of these various parts theleg in FIG. 9 is shown as though the graft material were transparent.The stents are formed from a shape set laser cut tube, similar to thestents described above. Support stents are preferably formed to 11 mm indiameter, and are a single circumferential row of zigzags, preferably 10zigzags. These stents are formed with uniform width connections at theintersections of the struts, as in the above stent structures. Thesestents are preferably cut from tubing of 0.251 cm ID by 0.317 cm OD(0.099 in. ID by 0.125 in. OD). The strut widths are preferably about0.33 cm (0.013 in.) wide adjacent the two-strut intersections. Thestruts are preferably about 7 mm long.

[0081] Lower most support stent 42 has a tapered profile, having adiameter at one end the same as support stents 40, and a diameter at theother end matching the diameter of iliac stent 18.

[0082] Upper most support stent 41 for the ipsilateral leg, as shown indetail in FIG. 10, differs from support stents 40 in that it has eyelet92 on one of the upper strut connections. This eyelet is used tostabilize the position of the leg during deployment as will be describedin more detail in the delivery catheter section. The contralateral leghas a similar eyelet.

[0083] Stent Materials and Processing

[0084] Support stents 40, iliac stents 18 and 19, mid stent 30, as wellas aortic stent 10, preferably are self-expandable and typically arecomprised of a shape memory alloy. Such an alloy can be deformed from anoriginal, heat-stable configuration to a second, heat-unstableconfiguration. The application of a desired temperature causes the alloyto revert to an original heat-stable configuration. A particularlypreferred shape memory alloy for this application is binary nickeltitanium alloy comprising 55.8% Ni by weight, commercially availableunder the trade designation NITINOL. This NiTi alloy undergoes a phasetransformation at physiological temperatures. A stent made of thismaterial is deformable when chilled. Thus, at low temperatures (e.g.,below 20° C.), the stent is compressed so it can be delivered to thedesired location. The stent is kept at low temperatures by circulatingchilled saline solution. The stent expands when the chilled saline isremoved and it is exposed to higher temperatures within the patient'sbody, e.g., 37° C.

[0085] Preferably, each stent is fabricated from a single piece of alloytubing. The tubing is laser cut, shape-set by placing the tubing on amandrel, and heat-set to its desired expanded shape and size.

[0086] Preferably, the shape setting is performed in stages at 500° C.That is, the stents are placed on sequentially larger mandrels andbriefly exposed to 500° C. For most of the stents, at least twoincreasingly larger mandrels are required to set the final size withoutunduly stressing the stent. To minimize grain growth, the total time ofexposure to 500° C. is limited to 5 minutes. The stents are then giventheir final shape set for 4 minutes at 550° C., and then “aged” at 470°C. (to impart the proper martensite to austenite transformationtemperature), then blasted (as described below) before electropolishing.This heat treatment process provides for a stent that has a martensiteto austenite transformation which occurs over a relatively narrowtemperature range (e.g. 15 centigrade degrees).

[0087] To improve the mechanical integrity of the stent, the rough edgesleft by the laser cutting are removed by a combination of mechanicalgritblasting and electropolishing. The grit blasting is performed toremove the brittle “recast” layer left by the laser cutting process.This layer is not readily removable by the electropolishing process, andleft intact, could lead to brittle fracture of the stent struts. Asolution of 70% methanol and 30% nitric acid at a temperature of −40° C.or less has been shown to work effectively as an electropolishingsolution. Electrical parameters of the electropolishing are selected toremove approximately 0.00127 cm (0.0005 in.) of material from thesurfaces of the struts. The clean, electropolished surface is the“final” desired surface for attachment to the graft materials. Thissurface has been found to impart good corrosion resistance, fatigueresistance, and wear resistance.

[0088] Graft Material Components

[0089] Graft material 45 of trunk 12, branches 14 and 16, and legs 15and 17 may be made of materials which include woven, knitted, sintered,extruded, or cast materials comprising polyester,polytetrafluoroethylene (PTFE), silicones, urethanes, andultralight-weight polyethylene, such as that commercially availableunder the trade designation SPECTRA™. The materials may be porous ornonporous. Preferred material includes a woven polyester fabric madefrom DACRON™ or other suitable PET-type polymer.

[0090] A preferred fabric for the graft material is a 40 denier 27filament polyester yarn, having about 70 to 100 end yarns per cm perface (180 to 250 end yarns per inch per face) and 32 to 46 pick yarnsper cm per face (80 to 120 pick yarns per inch per face). At this weavedensity, the graft material is relatively impermeable to blood flowthrough the wall, but yet is relatively thin, ranging between 0.08 and0.12 mm wall thickness.

[0091] The graft material for trunk 12 is preferably woven as a seamlessbifurcating weave, woven flat on a standard Dobby loom. Preferably ataper is incorporated between the single lumen upper portion of thewoven graft trunk and the two smaller diameter lumens. To enable thistaper, the pick (weft) yarns are interwoven around every two warp yarns.This allows for a tight relatively impermeable weave for the upperportion of the trunk, and the ability to “pack” the weave even moredensely for the tapering portion and the two branches.

[0092] The graft material of legs 15 and 17 preferably are woven of thesame material as trunk 12. These graft components are single lumentubes, and preferably have a taper and flared portion woven directlyfrom the loom, as illustrated for leg 15 in FIG. 9.

[0093] Prior to attachment of the stents, crimps are formed in the trunkand leg graft components between the stent positions by placing thegraft on a shaped mandrel and thermally forming indentations in thesurface. Preferably, crimps 41 (as shown in FIGS. 4 and 5) in the graftare about 2 mm long and 0.5 mm deep. With these dimensions, the graftsystem, with the support stents 40 attached, can bend and flex, yetmaintain an open lumen.

[0094] Also prior to attachment of aortic stent 10 to trunk 12, thegraft material of trunk 12 is cut in a shape to mate with the aorticstent (i.e., in a zigzag pattern). Preferably, the caudal ends of theleg grafts are also shaped to match the iliac stent. Attachment of StentComponents and Graft Components Each stent (i.e., aortic stent,mid-stent, iliac stent, and support stents), is attached to theappropriate graft component with suture material. The suture material ispreferably polyester braided 5/0 surgical suture impregnated with PTFE(polytetrafluoroethylene) strands. A preferred suture material is SilkyII Polydeck™ by Genzyme.

[0095] The method of suturing stents in place is important forminimizing the relative motion or rubbing between the stent struts andthe graft material. Because of the pulsatile motion of the vasculatureand therefore the graft system, it is possible for relative motion totake place, particularly in areas where the graft system is in a bend,or if there are residual folds in the graft material, due to beingconstrained by the aorta or iliac arteries.

[0096] Ideally, each strut of each stent is secured to graft material bysuture thread. A preferred type of stitch is a “blanket stitch”, whichserves to securely holds the struts at numerous points against the graftmaterial. A secure hold is desirable in preventing relative motion in anenvironment in which the graft system experiences dynamic motion arisingfrom pulsatile blood pressure, in addition to pulsation of the arteriesthat are in direct mechanical contact with the graft system. The strutsnearest the aortic and iliac ends of the graft system are subject to thepulsatile motion arising from arterial contact. These struts inparticular should be well secured to the graft components. It isdifficult to manipulate the suture thread precisely around struts thatare inside the graft component (i.e., some distance away from an openend), so various stitches, or none at all, may be used there.

[0097] As shown in FIG. 3, the lower struts in the aortic stent aresecured to the cranial end of the graft material of trunk 12, which hasbeen cut to match the shape of the stent. The blanket stitchingcompletely encircles the strut and “bites” into the graft material.Preferably, the stitch encircles the strut at approximately five equallyspaced locations. The struts are positioned on the outside of the graftmaterial for this particular attachment, however, the struts could bepositioned on the inside surface as well.

[0098] The mid-stent also is secured to the aortic graft component withthe use of blanket stitching. The upper and lower zigzag patterns ofstruts on each end of the mid-stent are secured in this fashion.Individual point stitches are used to secure the middle strutintersections to the inside surface of the graft component.

[0099] For the attachment of the support stents into the trunk graftmaterial, as well as each of the leg graft components, the ends of thestents are secured via individual point stitches at several positionssuch as 37, as shown in FIG. 3B.

[0100] Once the graft system is fully implanted into the aneurysm, theaortic and iliac ends of the graft system will be in direct contact withthe blood vessel, and therefore subject to the pulsatile motion of thoseblood vessels. However, a significant length portion of the implantedgraft system will not rest directly against vascular tissue. Thisportion of the graft system will be within the dilated aneurysm itself.Therefore, this portion of the graft system will not experience anysignificant pulsatile motion. For this reason, it is not necessary tosecure these stents to the graft material as aggressively as the stentstructures described above. Therefore only point stitches are necessaryfor securing the support stents.

[0101] Although not shown in the figures, iliac stents are secured tothe graft material by means of sutures, preferably blanket stitching, atthe upper and lower zigzags.

[0102] Graft Delivery System

[0103] In the preferred embodiment of the graft system, two separatedelivery catheters are utilized to deliver the three graft structures.The first delivery catheter 110, as shown in FIGS. 12-18 is used todeliver the aortic trunk and a first leg. This delivery system isreferred to as the “ipsilateral” delivery system. A second deliverycatheter (“contralateral” delivery system) is used to deliver the secondleg graft into the second branch of the aortic trunk, and is deliveredfrom the opposite femoral artery as the first delivery system.

[0104]FIG. 12 is a view of the delivery catheter 110 including outersheath 112 and handle 116. FIG. 13 is a view of the distal portion ofthe same catheter with the outer sheath 112 fully retracted to exposeinner catheter 114. Outer sheath 112 and inner catheter 114 areconnected to handle 116. Handle 116 at the proximal end of the deliverysystem causes relative sliding motion between sheath 112 and innercatheter 114 to facilitate delivery of the graft structures as will bedescribed more fully hereafter with respect to FIG. 16. The graftstructures (which are not shown in FIGS. 12-18) are positioned in afolded and compressed state in an annular space between outer sheath 112and inner catheter 114, toward the distal end of the delivery system.

[0105] The handle contains three fluid delivery ports 120, 122, and 124as shown in FIG. 12. First port 120 communicates with balloon structure126 near the distal end of the inner catheter, second port 122communicates with the lumens 123 defined by a saline delivery tube 160(FIG. 15B), for delivery of chilled saline, and third port 124communicates with an outlet 125 (FIG. 18) on the inner catheter fordelivery of radiopaque contrast media. These fluid delivery paths willbe discussed in more detail below.

[0106] Referring to FIG. 12, outer sheath 112 is positioned with itsdistal tip 113 overlapping an inflated balloon 126. The inflated balloonprovides for a smooth tapering transition for the outer sheath. Thiswill be described in more detail below. In this configuration, with thegraft structures loaded in a folded and compressed state, the catheteris introduced into the patient's vascular system for delivery of thegraft structures.

[0107] Inner Catheter

[0108] Inner catheter 114 and handle 116 are shown in FIGS. 12 and 13.Near the distal end is a composite balloon tip structure. The inflatableballoon 126 is inflated during introduction of the delivery catheterinto the vasculature and to the desired delivery site within theaneurysm. The balloon is attached to a balloon catheter shaft 128. Thisballoon catheter shaft runs the entire length of the delivery catheterand attaches to the handle mechanism near the proximal end. The proximalend of the handle mechanism is non-moving/non-rotating. The ballooncatheter shaft has a lumen 194 the entire length for passage of aconventional 0.089 to 0.96 cm (0.035 or 0.038 in.) diameter guidewire.An additional pathway 196 in the balloon catheter shaft carriesinflation media to the balloon for inflation and deflation through port198. The inflated balloon is preferably slightly larger in OD, than thesheath ID, to assure a smooth tight fit. The inflated balloon preventsthe leading edge of the outer sheath from “catching” or “snagging” onthe walls of the vasculature. The balloon tapers at both ends, and ispreferably fabricated of a relatively non-compliant polymer such asnylon. The balloon is preferably about 3 cm in length.

[0109] On the outside of the balloon catheter shaft is a distal taperingtransition 130, hereafter referred to as DTT. The DTT preferably isfabricated from an elasomeric copolymer commercially available under thetrade designation PEBAX from Elf Atochem. The DTT provides a transitionin flexibility from the distal-most portion of the inner catheter, toand through the balloon structure. When the delivery system is beingadvanced into and through tortuous vasculature, the DTT helps guide andflex the relatively stiffer outer sheath over the more flexibleguidewire and around bends in the vasculature. Without this structure,there would be an abrupt transition in stiffness between the guidewireand the stiffer sheath, and trackability through curves would be greatlyinhibited. FIG. 15A is a cross-sectional view of the inner catheteralong line a-a through the middle portion of the balloon. Balloon 126,DTT 130, and balloon catheter shaft 128 can be seen.

[0110] Proximal to balloon 126, DTT 130 tapers inwardly to a smallerdimension. The aortic stent is disposed about this region of thetransition element when loaded in the delivery catheter. To minimize thechance of kinking during advancement and tracking of the deliverysystem, it is desirable to maintain a relatively uniform lateralstiffness along the length of the loaded delivery catheter, with onlysmooth, gradual changes in stiffness. Without the proximal portion ofthe transition element in place, the delivery system could have a weak,kink prone region just proximal to the inflated balloon, and thereforethe presence of the transition element helps prevent kinking of thesheath.

[0111] Further proximal to the tapering transition element, the ballooncatheter shaft is supported by a distal reinforcing tube 162, preferablyof polyimide having a wall thickness of about 0.0035 inches (0.0014 cm)and an outer diameter of about 0.09 inches (0.035 cm). It is in thisregion where the bifurcated upper graft trunk resides when the deliverycatheter is loaded. When loaded in the delivery catheter, the folded andcompressed graft material in this region adds stiffness when compared tothe region with the aortic stent. Therefore, a lower stiffness isrequired for the inner catheter in this region than in the region closerto the balloon 126. The inner catheter in this region comprises ballooncatheter shaft 128, and thin walled tube 162, attached to the outside ofthe balloon catheter shaft.

[0112] Proximal to the folded and compressed aortic trunk (attached tothe aortic stent) in the delivery system is proximal tapering transitionelement 132, hereafter referred to as PTT. The distal end of PTT 132 isfixed about the outside of the balloon catheter shaft as can be seen inFIG. 18 which is an enlarged view of a portion of the inner catheterincluding the PTT and the stabilizing mechanism. The distal end of PTT132 has a tapering diameter from the OD of the balloon catheter shaft toa diameter approximately equal to the ID of the distal end of the outersheath. Following delivery of the aortic trunk component, the distal endof the outer sheath rests on the maximum diameter region of PTT 132. Theentire delivery catheter is then advanced into the aortic trunk untilthe desired position for delivery of the ipsilateral leg component isreached. The tapering diameter of the distal end of PTT 132 facilitatesthe advancement of the delivery catheter, minimizing any “snagging” or“catching” of the distal tip of the outer sheath on the inside of theaortic trunk graft material.

[0113] On the major diameter portion of PTT 132 is series oflongitudinal grooves 168. These grooves provide an outlet for thechilled saline that is infused on the inside of the outer sheath duringdelivery, to keep the shape memory stent components in a compressedstate.

[0114] Proximal to the PTT is a stabilizing mechanism 135 for securelyholding the distal position of the ipsilateral leg during delivery. Itis important for the ipsilateral leg to be maintained longitudinallytaut while the outer sheath is being withdrawn. This is accomplished bymeans of a stabilizing wire, which keeps the upper-most stent in theipsilateral leg graft from migrating proximally in the delivery catheterduring sheath retraction. If this stent is not prevented from migrating,and it does migrate during sheath retraction, the leg will compactlongitudinally in the delivery system, and once it is fully exposed andexpanded, the blood pressure inside the graft will re-lengthen it, andthe combined aortic trunk and leg will be longer than desired. The extralength will cause the ipsilateral leg graft to “bow” or “snake” insidethe aorta and iliac arteries, which is undesirable.

[0115] The stabilizing mechanism consists of clip 136 and stabilizingwire 138 that runs through clip 136. The upper-most stent of the leggraft has an eyelet attached to one of the struts, as shown in FIG. 9B.attached to one of the struts. When loaded in the delivery catheter, thestabilizing wire passes through the eyelet. The stabilizing wire runs inlumen 170, as shown in FIG. 18. This lumen is defined by a protectorsheath 172 which surrounds the stabilizing mechanism, and has an opening174 for the clip and a portion of the stabilizing wire. Just distal ofthe clip is where the eyelet of the upper stent is positioned. Theeyelet and stent are then securely positioned between the clip and thelumen which contains the stabilizing wire farther proximally.

[0116] Once the delivery catheter is positioned in the proper positionwithin the aneurysm, the outer sheath is retracted relative to the innercatheter, and the folded compressed graft segments. The aortic trunk isexposed, and expands into position in the aneurysm. The deliverycatheter is then advanced into this trunk until the lower end of theipsilateral leg component is in proper position, relative to theinternal iliac artery. This assessment is aided by introducing contrastfluid into the vasculature via the contrast delivery port. Oncepositioned, the outer sheath is then withdrawn further via manipulationof the delivery handle. As the ipsilateral leg is exposed, the upper endbegins to expand within the branch of the aortic trunk graft. Thestabilizing wire is still engaged into the eyelet of the upper supportstent.

[0117] As best seen in FIG. 16, the outer sheath is retracted bymanipulating a rotating knob 176 which rotates threaded rod 178. Outersheath 112 is connected to outer sheath mount mechanism 180. Rotation ofknob 176 causes threaded rod 178 to move outer sheath mount mechanism180 proximally. When mechanism 180 reaches pin 182 the aortic trunkgraft component has been deployed. Pin 182 is then removed to allowdeployment of the ipsilateral leg component of the graft system onceadvanced within the trunk to the proper location. Once the sheath iswithdrawn to the location of the iliac stent, mechanism 180 engagesactuator 184 and begins to move it proximally, together with the outersheath. Actuator 184 is connected to stabilizing wire 138 which is alsocaused to be withdrawn. The stabilizing wire is threaded through theeyelet at a location just distal of the clip. As the stabilizing wire iswithdrawn it is retracted through the eyelet. The stabilizing wire isfully disengaged from the eyelet just prior to full exposure andexpansion of the iliac stent. The delivery catheter can now be removedfrom the ipsilateral vasculature.

[0118] Referring again to FIG. 13 and FIG. 15B, proximal to thestabilizing mechanism on the inner catheter, the inner catheter shaftcontains proximal support tube 164. This tubing defines the contrastlumen 166, which leads into the PTT and out the port 125. This tubingcomponent is placed coaxially surrounding the polyimide stiffeningtubing 162 already described, and extends proximally. While defining thecontrast lumen, this tubing also adds additional stiffness to the innercatheter, over and above the stiffness provided by the balloon cathetershaft and the polyimide shaft. This additional stiffness “makes up” forthe lower stiffness of the compressed and folded ipsilateral legcomponent, such that the stiffness of the delivery system is maintainedrelatively the same as the stiffness distally. Preferably this tubingcomponent is comprised of a rigid material, such as polyetherethylketone(PEEK), or polyimide.

[0119] Proximal to the region holding the ipsilateral leg is theproximal shaft region of the inner catheter, shown in FIG. 15B. Theinner catheter in this region has an additional component, the salinedelivery tube. FIG. 15B is a cross section showing the construction ofthe delivery catheter in this region. The saline delivery tube iscoaxially positioned about the other tubular structures of the innercatheter, and contains a central lumen, inside of which are tubes 162,164, and the balloon catheter shaft 128. The contrast lumen 166described above is defined by the space between the proximal supporttube 164 and the distal support tube 162. There are preferably sixlumens within the wall of the saline delivery tube, five of which areused to deliver chilled saline into the outer sheath, and over thefolded compressed graft components when loaded into the deliverycatheter. The stabilizing wire 138 resides in the other lumen 170, andextends proximally into the delivery handle mechanism. The salinedelivery lumens 123 exit into the annular space between the innercatheter and the outer sheath at the distal end of the saline deliverytube.

[0120] The saline delivery tube is preferably constructed ofpolyethylene, and is sized to fit closely to the inner diameter of themain sheath. In this fashion, the saline delivery tube adds stiffness tothe completed delivery catheter, and the size prevents potential kinkingof the outer sheath in this region of the catheter.

[0121] The distal and proximal support tubes 162 and 164 indicated inFIG. 15B extend only a few cm proximal of the distal end of the salinedelivery tube. The proximal support tube is adhesively bonded to theinner surface of the central lumen of the saline delivery tube, and thepolyimide tube is adhesively bonded to the outer surface of the ballooncatheter shaft. The proximal shaft of the balloon catheter is connectedto the delivery handle in a fashion which fixes its position withrespect to the outside of the delivery handle.

[0122] Outer Sheath

[0123] The outer sheath preferably has three different layers, as shownin FIG. 17, which is a view of the distal tip of the outer sheath. Theinner lining 186 of the sheath is preferably polytetrafluoroethylene(PTFE), to minimize friction of the sheath as it retracts from thefolded and compressed graft components. The outer layer 188 ispreferably cross-linked heat-shrinkable polypropylene, to minimizefriction of the outside against the vasculature, and provide highlongitudinal rigidity (to prevent stretching during sheath retraction).An intermediate layer 190 is low density polyethylene, which when heatedto near its melting temperature, fuses the polypropylene to the PTFE.The PTFE has an etched exterior surface to facilitate adhesion of theLDPE to the polypropylene.

[0124] At the distal tip, as shown in FIG. 17, the outer orpolypropylene tube 188 is projected and beveled down beyond the PTFE andmiddle layers. This allows for the very tip to present a very thin“profile” atop the inflated balloon of the inner catheter. This helps tominimize the chance of the tip snagging during advancement of thedelivery system in the vasculature. Additionally, after the outer sheathhas been withdrawn to the proximal transition element 132, the leadingedge again presents a very low profile, minimizing the chances ofsnagging.

[0125] In a preferred embodiment, the sheath is sized to the graft size,and could be, for instance, approximately 0.599 cm (0.236 in.) ID by0.676 cm (0.266 in.) OD. The projecting tip is beveled inward to an IDof approximately the same 0.599 cm (0.236 in.).

[0126] Alternative materials for the sheath and tip construction arealso contemplated. For example, an elastomeric material could be usedfor the outer layer of the sheath, or for just a distal portion of theouter layer of the sheath, and could be formed to a smaller innerdiameter, for example 0.584 cm (0.230 in.) In this fashion, the tipwould fit snugly against the PTT when the sheath is withdrawn, furtherlowering the profile of the sheath tip, and further minimizing snaggingor hanging up during subsequent advancement of the delivery catheter.Furthermore, the elastomeric material could be filled with a radiopaquefiller such as barium sulfate, particularly if it is only applied at thedistal tip of the outer sheath. The overall length of the outer sheathis 54 cm from the delivery handle to the distal end of the outer sheath.

[0127] Delivery Handle

[0128] The handle is shown in cross section in FIG. 16. The innercatheter is attached to the delivery handle near the proximal end. Theouter sheath is attached to the delivery handle at outer sheath mountmechanism 180, which is actuated by rotation of a rotating knob 176,near the proximal end. The outer sheath mounting mechanism 180 travelsalong a threaded rod inside a housing 192. The rotation of the rotatingknob (relative to the housing and the inner catheter) rotates thethreaded rod, which draws back the outer sheath. A pin 182 projects intothe housing which stops the motion of the outer sheath after the aortictrunk graft is delivered. This pin prevents inadvertent deployment ofthe ipsilateral leg, until proper positioning is attained. The pin isremoved following advancement and proper positioning of the ipsilateralleg component. Once the pin is removed, the outer sheath con continue tobe retracted to expose the self-expanding ipsilateral leg graft.

[0129] Contralateral Leg Delivery System

[0130] Once the aortic trunk graft component and the ipsilateral leggraft component are delivered, the contralateral leg is delivered viathe contralateral femoral artery. The contralateral leg graft component,as described above is preferably identical in construction to theipsilateral leg component. However, since this is the only graftcomponent being delivered on the contralateral side, the deliverycatheter is somewhat different.

[0131] The contralateral delivery catheter is also comprised of an innercatheter, an outer sheath, and a delivery handle, and in many ways, thestructure is quite similar. The inner catheter has a similar balloon tipconstruction, but it is smaller in diameter, since the delivery catheteronly needs to contain the lower profile contralateral leg graftcomponent.

[0132] The outer sheath is also smaller, preferably about 0.508 cm by0.564 cm (0.200 in. by 0.222 in.). It is fabricated of a single layer ofPTFE.

[0133] Since there is only one leg graft component, there is no proximaltaper transition element for this delivery catheter, so the constructionof the inner catheter is similar, with the exception of the regioncontaining the proximal taper transition element. There is a legstabilizing mechanism, similar to that on the ipsilateral deliverycatheter which is positioned immediately proximal to the balloon. Thestabilizing mechanism functions in the same manner as that for theipsilateral delivery catheter.

[0134] Additional Embodiments

[0135] While the above graft system, with the trans-renal aorticattachment structure, is contemplated for use in a variety of anatomicconditions, particularly those with shorter necks, and those withtortuous aortas above the aneurysm, a somewhat different embodiment iscontemplated for aneurysms with longer, and/or less tortuous aorticnecks.

[0136] In this embodiment, the structure of the graft components anddelivery catheter is identical with one exception. This “nontrans-renal” design has no bare stent structure above the upper edge ofthe graft material. Barbs would be present (such as shown at 58 in FIG.6A), but the aortic attachment stent would consist of only a singlecircular zigzag of struts, joined to the upper edge of the graftmaterial via sutures, preferably by blanket stitching.

[0137] The advantage of this design for the graft system is that inrelatively long necks, e.g., longer than 3 cm, there is little need forthe extra securement provided by the above “trans-renal” structure, soutilizing a structure with no “trans-renal” structure presents nointerference with the renal arteries.

[0138] Aortic Cuff

[0139] It is contemplated that in some instances, the aortic graftsystem embodiments described above may be inadvertently positioned toolow in the aorta, leaving too little overlap with the “healthy” aorta ofthe upper neck of the aneurysm to form a robust seal. This erroneousplacement has been observed with other endovascular grafting systems.

[0140] To help mitigate this problem, a short piece of graft materialwith an internal stent is contemplated. This is shown in FIG. 19. This“aortic” cuff is the same diameter as the already placed aortic trunkgraft, but would be short, e.g. 2 to 4 cm in length. FIG. 19 is aperspective view of an aortic cuff. Inside is a self-expanding stentstructure similar to the mid-stent, but with a cylindrical shape. Theaortic cuff is implanted in an overlapping fashion inside the upper endof the aortic trunk, with a small length of aortic cuff projecting abovethe upper edge of the aortic trunk, to effectively result in a longertotal overlap with the aortic neck. The aortic trunk is delivered via adelivery system similar to the contralateral leg delivery system. Asimilar inner catheter with a balloon tip, and outer sheath retractablevia a delivery handle is utilized. Unlike the contralateral leg deliverysystem, however, the wire stabilization mechanism is positioned proximalto where the compressed and folded aortic cuff would reside in thedelivery system. The eyelet 202 on the aortic cuff is on the caudalside, and engages with the wire stabilizing mechanism when loaded in thedelivery catheter. By locating the stabilization mechanism on the caudalend of the aortic cuff, the aortic cuff is prevented from “jumping” outof the delivery catheter once the outer sheath is partially withdrawn,without stabilizing the caudal end, the relatively large diameter andrelatively short length would cause the aortic cuff to “jump” craniallyduring delivery, resulting in mis-positioning.

[0141] It has been observed that any motion of stent structure againstgraft material can lead to graft wear, and subsequent holes. Since theaortic cuff structure would overlap on the inside of the aortic trunk,in an area with substantial motion set up by the aortic pulsatility,there is potential for relative motion to exist between these twostructures. The “weak link” in this overlapped area is the graftmaterial of the aortic cuff. The stent structure of the aortic trunk isable to have some small but significant relative motion, wearing a holethrough the aortic cuff. After a hole is worn, the stents of the cuffand the trunk can rub against each other, causing subsequent failure ofthe struts.

[0142] To prevent such premature wearing of the graft material of thisaortic cuff, it is contemplated to have two layers of graft material. Ina preferred embodiment, two layers of the graft material described abovewould be sutured, preferably by blanket stitching, to the outside of thestent structure, in a manner similar to the attachment of the mid stentto the aortic trunk graft material. By utilizing two layers, the amountof time required to wear a hole through the graft material issignificantly extended.

[0143] Although particular embodiments of the invention have beendisclosed herein in detail, this has been done for the purposes ofillustration only, and is not intended to be limiting with respect tothe scope of the appended claims. It is contemplated that varioussubstitutions, alterations, and modifications may be made to theembodiments of the invention described herein without departing from thespirit and scope of the invention as defined by the claims.

What is claimed is:
 1. An endovascular graft system capable of beingdeployed at a desired location within a vessel, the endovascular graftsystem comprising: an aortic stent, having first and second ends; atrunk formed of a graft material having an interior surface defining alumen, the trunk being affixed to the second end of the aortic stent;and a plurality of stents affixed to and supporting the interior surfaceof the trunk, the plurality of stents being spaced apart such that fullyunsupported regions of the trunk lie between adjacent stents; the graftmaterial of the trunk being affixed to the aortic stent and to theplurality of stents in a manner which limits movement of the graftmaterial with respect to the aortic stent and the plurality of stents.2. The endovascular graft system of claim 1 wherein the graft materialof the trunk is crimped toward the lumen in the unsupported regionsbetween stents.
 3. The endovascular graft system of claim 1 wherein thetrunk has first and second branches configured such that the lumencomprises a main lumen and first and second branch lumens and whereinthe plurality of stents includes a first stent located in the main lumenbetween the aortic stent and the first and second branch lumens and aplurality of second stents located in the first and second lumens.
 4. Astent for placement in a vessel of a patient's vascular systemcomprising: a substantially tubular body portion having a plurality ofstruts, each strut having first and second ends and a midpoint locatedmidway there between, each end of the plurality of struts intersectingwith an end of at least one adjacent strut to form a plurality of strutintersections, at least one strut being configured to taper between themidpoint and the first and second ends in a manner that is gradual andsubstantially continuous.
 5. The stent of claim 4 wherein the tubularbody portion defines a longitudinal axis and has a first end and asecond end and wherein a plurality of intersecting struts adjacent thefirst end form a substantially diamond shape pattern at the first end ofthe stent and a plurality of intersecting struts adjacent the second endform a substantially zigzag pattern at the second end of the stent, thediamond shape pattern and zigzag pattern being connected by a pluralityof longitudinal struts, the longitudinal struts being substantiallyparallel to the longitudinal axis of the tubular body, and wherein theat least one strut being configured to taper is a strut adjacent thefirst end of the stent.
 6. The stent of claim 4 wherein the at least onestrut being configured to taper includes the plurality of strutsadjacent the first end of the stent.
 7. The stent of claim 4 wherein theat least one strut configured to taper is configured to taper from alarger dimension at the midpoint to smaller dimensions at the first andsecond ends.
 8. The stent of claim 4 wherein the at least one stentconfigured to taper is configured to taper from a smaller dimension atthe midpoint to larger dimensions at the first and second ends.
 9. Adelivery catheter for delivering and deploying an endovascular graftsystem at a desired location within a vessel of a patient's vascularsystem comprising: a handle; a shaft having a distal end and a proximalend, the proximal end being connected to the handle, the shaft having anouter surface and defining an inflation lumen and a guidewire lumen; aballoon attached at a location spaced from a distal end of the catheter,the balloon having an interior in fluid communication with the inflationlumen; a transition element affixed to the balloon, the transitionelement having a distal portion between the balloon and distal end ofthe catheter, the distal portion being configured to provide increasingstiffness from the distal end of the catheter to the balloon, the shaft,balloon and transition element together forming a portion of an innercatheter; an outer sheath defining a lumen containing the innercatheter, the outer sheath configured to move from an unretractedposition to a retracted position, the outer sheath having a distal endpositioned about the balloon when in the unretracted position.
 10. Thedelivery catheter of claim 9 wherein the distal portion of thetransition element tapers outwardly from the distal end of the catheterto the balloon.
 11. The delivery catheter of claim 9 wherein the lumenof the outer sheath has a first diameter at the distal end of the outersheath and wherein the balloon when inflated has a second diameter andwherein the second diameter is greater than the first diameter.
 12. Adelivery catheter for delivering an endovascular graft system at adesired location within a vessel of a patient's vascular systemcomprising: a shaft; a first graft component positioned about the shaft;a second graft component positioned about the shaft, the first graftcomponent being positioned distally of the second graft component, thefirst graft component being configured to be deployed in the vesselprior to deployment of the second graft component, the first and secondgraft components each having proximal and distal portions, the distalportion of the second graft component being configured to be deployedwithin the proximal portion of the first graft component; a retractablesheath defining a lumen containing the shaft and first and second graftcomponents, the sheath being configured to deploy the first graftcomponent when the outer sheath is withdrawn a first distance and todeploy the second graft component when the outer sheath is withdrawn asecond distance; and means for stabilizing the position of the distalportion of the second graft component with respect to the proximalportion of the first graft component when the sheath is being withdrawnthe second distance.
 13. A delivery catheter for delivering anendovascular graft system at a desired location within a vessel of apatient's vascular system comprising: a handle; a shaft connected to thehandle; a first graft component positioned about the shaft; a secondgraft component positioned about the shaft, the first graft componentbeing positioned distally of the second graft component, the first graftcomponent being configured to be deployed in the vessel prior todeployment of the second graft component, the first and second graftcomponents each having proximal and distal portions, the distal portionof the second graft component being configured to be deployed within theproximal portion of the first graft component, the distal portion of thesecond graft component having a fastening element; a retractable sheathdefining a lumen containing the shaft and first and second graftcomponents, the handle being configured to retract the sheath to deploythe first graft component when the outer sheath is retracted a firstdistance and to deploy the second graft component when the outer sheathis retracted a second distance; and a stabilizing element connected atone end to the handle and at another end to the fastening element of thesecond graft component, the handle stabilizing element and fasteningelement being configured such that the stabilizing element is retractedin a manner that disconnects the stabilizing element from the fasteningelement when the second graft component is deployed.
 14. The deliverycatheter of claim 13 wherein the distal portion of the second graftcomponent includes a stent and wherein the fastening element is aneyelet fixed to the stent and the stabilizing element is a wire.